Precious metal powder, such as silver powder, is used in the electronics industry for the manufacture of conductive pastes. In the manufacture of solar cells, the conductive pastes are screen printed onto semiconductor substrates forming conductive patterns. These paste patterns are then dried and fired to volatilize and burn out the liquid organic medium and sinter the metal particles.
Capital investment for the furnace can be decreased because precious metals such as cold, silver, and palladium can be fired in air. Using precious metals, however, invites a sharp rise in material costs because precious metals are expensive:
Copper is widely used as a conductive component in semiconductor circuits and the like. Copper has the advantage of being less expensive than silver. However, copper cannot be fired in air because it oxidizes easily, and this increases capital investment because firing under a nitrogen atmosphere and the like is required.
Thus, in the process of forming solar cell electrodes and bus bars using conductive paste, the development of technology is needed that will satisfy the following requirements of: 1) enabling the use of inexpensive copper powder, 2) enabling firing to be performed in air, and 3) enabling low resistance in the electrodes.